linux-kernel - Re: [PATCH] mm: provide interface for retrieving kmem

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Message-ID: <80c402e5fa60cbe7c521c43103d3ee0e8a8c80eb.camel@oracle.com>
Date:   Fri, 08 Nov 2019 21:40:24 +0100
From:   Knut Omang <knut.omang@...cle.com>
To:     Christopher Lameter <cl@...ux.com>
Cc:     Michal Hocko <mhocko@...nel.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] mm: provide interface for retrieving kmem_cache name

On Fri, 2019-11-08 at 16:49 +0000, Christopher Lameter wrote:
> On Fri, 8 Nov 2019, Knut Omang wrote:
> 
> > On Fri, 2019-11-08 at 15:37 +0000, Christopher Lameter wrote:
> > > On Thu, 7 Nov 2019, Michal Hocko wrote:
> > >
> > > > On Thu 07-11-19 13:26:09, Knut Omang wrote:
> > > > > On Thu, 2019-11-07 at 12:58 +0100, Michal Hocko wrote:
> > > > > > On Thu 07-11-19 12:54:04, Knut Omang wrote:
> > > > > > > With the restructuring done in commit 9adeaa226988
> > > > > > > ("mm, slab: move memcg_cache_params structure to mm/slab.h")
> > > > > > >
> > > > > > > it is no longer possible for code external to mm to access
> > >
> > > That patch only affected the memcg_cache_params structure and not
> > > kmem_cache.
> > >
> > > And I do not see any references to the memcg_cache_param?
> >
> > Good point, I should have made explicit reference to it.
> >
> > It gets inlined into kmem_cache with CONFIG_SLUB if CONFIG_MEMCG is set
> > (include/linux/slub_def.h, line 112)
> 
> Yes but that does not affect the "name" field on line 105
> 
> > > The fields that all allocators need to expose are listed in
> > > the struct kmme_cache definition in linux/mm/slab.h.
> >
> > So I take that kmem_cache::name was still intended to be public,
> > just that that broke due to the inlining of struct memcg_cache_param
> > in slub_def.h?
> 
> The patch did not change the name field. I am not sure what is broken?
> 
> Maybe you need memcg_params to compose a name of the memcg with the slab
> name?

No, it's just that the slub definition of struct kmem_cache won't compile because
the definition of struct memcg_cache_params is no longer available.

Knut